Battery dies but then comes back again, all a bit weird?

[PieEater]

Someone will correct me if I'm wrong but you will still get at least the expected cold voltage readings even if you have a dead cell in the battery as the other cells will still be outputting the volts but not the amps. This was explained to me by a battery specialist when I couldn't understand why my battery optimiser was saying the battery voltage was OK but the battery still wouldn't crank over the engine. Needless to say a new battery resolved the issue.